If there are 4 cups in every quart, and there are 6 quarts, that mean there are 24 cups of milk. If you take 24 and divide it by 3 cups each, you will get 8 sets with 3 cups in each set. For every set, you need to add 2 eggs, so that would be 16 eggs for the total of 6 quarts. Answer is 16 eggs.
